Arc centering contact arrangement



Dec. 17, 1963 H, STETTQ R 3,114,814

ARC CENTERING CONTACT ARRANGEMENT Filed Sept. 18, 1961 PRIOR ART 4 Fig.2! t Fig.2: F294 I 5 r 3 PRIOR ART United States Patent C) "ce 3,114,814 ARC CENTERING CONTACT ARRANGEMENT Hubert Stettner, Neumunster, Germany, assignor to Licentia Patent-Verwaltung-G.m.b.H., Frankfurt am Main, Germany Filed Sept. 18, 1961, Ser. No. 138,953 Claims priority, application Germany Sept. 19, 1960 7 Claims. (Cl. 200-147) The present invention relates -to switches.

More particularly, the present invention relates to an electric contact arrangement, especially a U-shaped stationary contact for use in relays or other types of electric switches.

When the contacts of an electric switch are separated, an arc will usuall be formed. The arc starts at the point at which the surfaces of the contacts are last separated. The forces acting on the arc will be continuations of the resul-tants of the current lines flowing in the arc. If this arc is stanted not exactly along the center line of the contact element, these forces will drive the arc toward the edge of this contact element. The loop of the arc will then be extended and finally strike the lateral walls of the arc extinguishing chamber within which the contacts are located.

This behavior of the arc is decidely undesirable inasmuch as the walls of the arc extinguishing chamber are subjected to substantial forces. Furthermore, if the base points of the arc remain at the edge of the contact sur- 'face proper for relatively long periods of time, these edges will be severely scorched, partly because the rate at which heat is dissipated from the edges is slower than the rate at which the heat is dissipated from the fiat surface, and partly because only a small portion of the vaporized material is condensed back onto the contact surface.

It is, therefore, an object of the present invention to provide a contact arrangement which overcomes the above disadvantages, and this is accomplished by so constructing the lateral edges of the contact that, in the region of the actual contact surface, the edges are C-shaped and curve toward the actual contact surface. Due to this arrangement, a laterally moving arc is taken over by the curved contact edges. As soon as this are is in fact transferred to the curved edges, forces will act on the are which tend to drive it back onto the contact surface and which move the arc in a direction toward the middle of the contact so that the walls of the arc extinguishing chambers are eflectively relieved of the influences of the arc.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURES 1a and 1b are comparative sectional views of a prior art contact arrangement and of a contact ar rangement according to the present invention, respectively, showing the behavior of forces acting on the are formed upon contact opening.

FIGURES 2a and 2b also are comparative sectional views of the prior art contact arrangement and the contact arrangement according to the instant invention, respectively, showing the distribution of the electric potential in the space between the stationary and movable contacts.

FIGURE 3 is a plan view of a contact arrangement according to the present invention.

FIGURE 4 is a sectional view of another embodiment of a contact arrangement according to the present invention.

FIGURE 5 is a sectional view of a functional embodiment of the instant invention, taken substantially along line 5-5 of FIGURE 6.

FIGURE 6 is a plan view of the contact arrangement 3,114,814 Patented Dec. 17, 1963 of FIGURE 5, the arc extinguishing chamber housing the contact arrangement being shown in section.

Referring now to the drawings and FIGURES la, 1b, 2a, and 2b thereof in particular, the same show the walls 1 of an arc extinguishing chamber containing movable and stationary contacts 2 and 3 each of which is provided with a contact element proper indicated at 4. According to the present invention, as shown in FIGURES 1b and 2b, the lateral edge of the contact 3, which here includes a shoe '5 that is made of ferromagnetic material and is mechanically and electricall connected to the contact 3, is curved upwardly toward the element 4 carried by the contact 3.

When the contacts are separated, an are formed between the contacts elements 4 will usually travel to the edges 4a 7 thereof, and, as in the prior art contact arrangement illustrated in FIGURE 1a, this are will, under the influence of the force P bulge toward the wall 1 of the are extinguishing chamber as indicated at 6a. The arc burns near or even strikes on the wall. Such burning results in damage to the wall. According to the present invention, however, the arc will, as shown in FIGURE lb, be taken over by the upwardly curved shoe 5 secured to the contact 3 so that the latter is freed from the arc and, what is more important, the arc will loop inwardly as indicated at 6 b, under the influence of the force P thereby preventing the are from striking the wall 1.

FIGURES 2a and Zbshow equipotential lines of the electric field between the two'contacts. It will be seen that the arrangement according to the instant invention produces a homogeneous distribution of the electric field in the space along the edges of the contact 3. As a result, the electric field strength, which, in the prior art arrangement illustrated in FIGURE 2a, is normally very high in the region of the edges, is relatively small, thereby increasing the resistance of the contact arrangement to flashbacks.

FIGURE 3 shows a plan view of the above-described arrangement according to the present invention. It will be seen that the magnetic field, which due to the current in contact 3 is present in the space above the contact element 4, is so shaped that the force P caused by such magnetic field and acting on the arc will hold the arc in the middle of the contact.

-It is not essential that the contact be provided with separate contact pieces carrying upwardly bent shoes; instead, the contact 13, shown in FIGURE 4, may be formed with an upwardly curved edge portion 15 which is bent toward the contact element 14.

FIGURES 5 and 6 show a functional embodiment of a contact arrangement wherein a movable contact bridge cooperates with two stationary contacts constructed in accordance with the present invention, the entire contact arrangement being located within an arc extinguishing chamber. In this embodiment, the stationary contacts 23 are bent into U-sh-aped configuration and carry the 'C-shaped arc-guiding shoes 25 to which they are electricaily and mechanically connected, the arrangement being such that the edges of the shoes are bent upwardly in the region of the contact elements 24. As best seen in FIGURE 6, the rear portions 23a of the contacts 23, considered in the direction in which the are on the respective side is propagated, are elongations which form surfaces along which the respective arcs can run. The rear portions or flanges 25a of the shoes 25 embrace the elongations 23a and converge toward each other to form a narrow gap 28. The shoes 25 thus serve as are running horns.

The movable contact carrier 29 carries the contact bridge 22 whose contact elements 22a engage the contact elements 24 of the stationary contacts. The entire structure is locatedin an arc extinguishing chamber 21, which also contains suitable arc extinguishing 'bafiies 30.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A contact arrangement comprising, in combination:

(a) means having two spaced apart side walls which form an arc extinguishing chamber between themselves; and

(b) two cooperating and separable contact means located in said are extinguishing chamber, between which contact means an arc is formed upon their separation, at least one of said contact means having lateral edge portions which are bent in the direction toward the other of said contact means into a generally C-shaped configuration, each such edge portion 'bulging toward the nearest side wall of said are extinguishing chamber and thence back away from such side wall so as to have a free edge which is spaced further away from the nearest side wall than the bulging portion, said lateral edge portions extending longitudinally in the direction oat said one contact means, in consequence of which an are formed upon separation of said contact means and running along said one contact means will, upon seeking a free edge thereof, be forced away from the corresponding side wall and toward the middle of said are extinguishing chamber, thereby to prevent striking of the are against said side walls.

2. A contact arrangement as defined in claim 1 Wherein said edge portions of said one contact means have flanges which, as seen in the direction of propagation of the arc, converge to form a narrow gap.

3. A contact arrangement as defined in claim 1 wherein said one contact means comprises a contact element whose surface is engaged by the other of said contact means, and shoe means electrically and mechanically connected to said contact element, said shoe means having said generally c-shaped configuration to form said edge portion of said one contact means,

4. A contact arrangement as defined in claim 3 wherein said shoe means are made of ferromagnetic material.

5. A contact arrangement as defined inclaim 3 wherein said shoe means are detachably connected to said contact element.

6. A contact arrangement as defined in claim 5 wherein said contact element is a U-shaped flat element, said shoe means being connectable to said contact element at one leg of the U configuration.

7. A contact arrangement as defined in claim 1 wherein said one contact meansis a fixed contact and said other contact means is a movable contact.

References Cited in the file of this patent UNITED STATES PATENTS 2,538,370 Lerstrup- Jan. 16, 1951 FOREIGN PATENTS 267,515 Great Britain Nov. 17, 1927 368,645 Great Britain Mar. 10, 1932 695,642 Germany Aug. 29, 1940 601,838 Great Britain May 13, 1948 1,108,488 France Aug. 31, 1955 1,092,989 Germany Nov. 17, 1960 

1. A CONTACT ARRANGEMENT COMPRISING, IN COMBINATION: (A) MEANS HAVING TWO SPACED APART SIDE WALLS WHICH FORM AN ARC EXTINGUISHING CHAMBER BETWEEN THEMSELVES; AND (B) TWO COOPERATING AND SEPARABLE CONTACT MEANS LOCATED IN SAID ARC EXTINGUISHING CHAMBER, BETWEEN WHICH CONTACT MEANS AN ARC IS FORMED UPON THEIR SEPARATION, AT LEAST ONE OF SAID CONTACT MEANS HAVING LATERAL EDGE PORTIONS WHICH ARE BENT IN THE DIRECTION TOWARD THE OTHER OF SAID CONTACT MEANS INTO A GENERALLY C-SHAPED CONFIGURATION, EACH SUCH EDGE PORTION BULGING TOWARD THE NEAREST SIDE WALL OF SAID ARC EXTINGUISHING CHAMBER AND THENCE BACK AWAY FROM SUCH SIDE WALL SO AS TO HAVE A FREE EDGE WHICH IS SPACED FURTHER AWAY FROM THE NEAREST SIDE WALL THAN THE BULGING PORTION, SAID LATERAL EDGE PORTIONS EXTENDING LONGITUDINALLY IN THE DIRECTION OF SAID ONE CONTACT MEANS, IN CONSEQUENCE OF WHICH AN ARC FORMED UPON SEPARATION OF SAID CONTACT MEANS AND RUNNING ALONG SAID ONE CONTACT MEANS WILL, UPON SEEKING A FREE EDGE THEREOF, BE FORCED AWAY FROM THE CORRESPONDING SIDE WALL AND TOWARD THE MIDDLE OF SAID ARC EXTINGUISHING CHAMBER, THEREBY TO PREVENT STRIKING OF THE ARC AGAINST SAID SIDE WALLS. 